For adhering an adherend material made from a hard raw material such as metal or ceramics and an adhesive material made from a soft raw material such as silicone rubber, physical adhesion by molecular interaction on the adhesive interface of the materials or chemical adhesion by formation of chemical bond thereon is performed.
As such physical adhesive method, a mechanical adhesive method in which the texture of the surface of an adherend material is roughened in order to increase its contacting area to an adhesive material is known. As such chemical adhesive method, an adhesive method using an adhesive agent in which a heat-hardening adhesive agent is applied to an adherend material and then an adhesive material is pressed against the adherend material is known. A surface treatment method in which a reactive group is introduced onto the surface of an adherend material by the surface treatment and then the adherend material binds chemically to the surface molecule of an adhesive material is also known as another chemical adhesive method. Also, Japanese Patent Provisional Publication No. 2006-198797 discloses another method of improving the reactivity of vinyl group with silicone rubber by a treatment of applying a vinyl compound to the surface of metal. In addition, it is also known as another method that liquid composition for silicone rubber of vinyl group-containing polysiloxane, hydrosilyl group-containing polysiloxane and a silane coupling agent such as platinum catalyst suspension is applied to the surface of platy a metal, which is washed with detergent, in order to harden the liquid composition to generate thereof as silicone rubber and simultaneously the silicone rubber is adhered to the metal.
An adhesive article prepared by the mechanical adhesive method comes unstuck easily. Adhesive strength of an adhesive article prepared by the adhesive method using the adhesive agent decreases due to deterioration of the adhesive agent caused by hard heat cycle or elapse of long time because the adherend material and the adhesive material are not chemically-bound on the interface thereof directly. While an adhesive article prepared by the surface treatment method is generally able to accomplish relatively strong adhesive strength by the formation of only two to four chemical bonds per 10,000 atoms on the surface of the adherend material and also the adhesive strength thereof does not receive environmental influence by temperature or solvent, it is difficult to definitively form chemical bond on the interface of the adherend material and the adhesive material and therefore a choice of a raw material for these materials is highly limited. Consequently, the surface treatment method lucks versatility.
In these conventional adhesive methods, if the adhesive material is made from silicone rubber, not only the intensity thereof is weak, but also adhering an adherend material and the adhesive material is difficult and, even if the materials are adherend, the adhesive strength thereof is weak. This is because the reactivity or the interaction of the silicone rubber with the surface of the adherend material on the interface thereof is poor. Therefore, it is necessary to adhere the silicone rubber of the adhesive material and the surface of the adherend material by an adhesive agent that well interacts with silicone rubber. However, the adhesive strength thereof is still not so sufficient.
Moreover, since thickness of the adhesive layer of the above-mentioned case is generally several μm to hundreds μm, the adhesive layer is capable of dispersing the stress from being pulled or bent but incapable of accomplishing sufficient adhesive strength as the amount of the adhesive agent thereof is too small. However, if the amount of the adhesive agent is increased to make the adhesive layer thicker, it results in strain concentration due to the stress that causes detachment of the materials, and the adhesive strength thereof decreases. It is difficult to balance the dispersion and concentration of stress by conditioning the amount of the adhesive agent in case of using an adhesive base material made from silicone rubber.
Furthermore, it is difficult to mutually adhere very small materials by the adhesive method using an adhesive agent.